The domestic cat serves as a model for 36 human physiological disorders ranging from hereditary dysfunctions to AIDS. Understanding the reproductive biology of the cat ensures the propagation of feline models useful for studying these conditions. This project focuses upon characterizing the reproductive biology of the domestic cat and its wild relatives. Although a wide array of events are studied (from sperm capacitation to implantation), the project concentrates on developing a fundamental understanding of fertilization and embryogenesis. Findings are relevant to (1) basic studies of fertilization mechanisms, gametogenesis, and early embryogenesis; (2) the reproductive consequence of teratospermia (the ejaculation of many malformed sperm, a condition common to both felids and humans); (3) application of learned technologies to propagation of genetically valuable laboratory animals and endangered species; and (4) genetic mapping studies and plans to deliver molecularly cloned genes into early-stage pre-implantation embryos. An additional benefit is the translation of the basic information into practical tools (especially artificial insemination [AI] and in vitro fertilization [IVF] embryo transfer) that are useful for producing genetically valuable laboratory cats, but also for preserving endangered species. AI has been successfully employed for propagating mucopolysaccharidotic cats and for producing domestic cat x leopard cat hybrids useful for developing a high resolution genetic linkage map of the domestic cat. The latter will be useful for further understanding the genetic loci involved in neoplastic transformation and other disease states. Assisted reproduction rates in cats parallel those derived for humans. Poor quality ejaculates and a large loss of embryos after transfer are common characteristics associated with the IVF system of both the cat and human. Therefore, the felid taxon serves as one of the most important non-primate models available for addressing these issues.